code: def forward(self, inputs, device):
      y = functions.hstack(inputs)
      return (y,)
  
file_path: chainer/tests/chainer_tests/functions_tests/array_tests/test_hstack.py
imports: import unittest
  import numpy
  import six
  from chainer import functions
  from chainer import testing
  from chainer.testing import attr
  from chainer.utils import type_check
label_desc: Use image node_id 2 for calling the TestHstack obj's underlying member method code with example usage: obj.forward(inputs, device) and returns: y